(1) Field of the Invention
The present invention relates to a cooling system for discharging the air heated in an electronic appliance having a heat source therein, such as an image forming apparatus using electrophotography.
(2) Description of the Prior Art
An image forming apparatus using electrophotography as an electronic appliance, typically includes a fixing unit for heating and fixing the toner image having transferred onto print media, a motor for the optical scanning device for recording a static latent image on the photoreceptor by scanning and other heat generating units.
In recent years, miniaturization of electronic appliances has been developed in order to minimize the space and footprint for installation. As a result, spaces between units inside the electronic appliance become narrower and adjacent units are designed so as to be laid out close to each other. This leads to a bad flow of air within the electronic appliance and hence to buildup of generated heat therein, thus raising the temperature of the electronic appliance as a whole.
Some units incorporated in an electronic appliance may lose their functions due to an elevated temperature. For example, in an image forming apparatus, a number of optical elements making up an optical scanning unit are laid out in the predetermined positional relationship with each other. In this system, if the positional relationship between these optical elements varies due to temperature variation, the image of light to be written on the photoreceptor will distort, making it impossible to produce a correct reproduction of an image.
To deal with such a situation, Japanese Patent Application Laid-Open Hei 4 No.257880 as a conventional example of an electronic appliance, has disclosed a configuration in which a cooling system for discharging the heat generated from heat generating units therein is provided so as to eliminate the influence of the heat upon the surrounding units.
However, some electronic appliances, such as an image forming apparatus having a fixing unit and an optical scanning unit, can include both a high-temperature unit to be maintained at a predetermined high-temperature state and a low-temperature unit which needs to be absolutely prevented from rising in temperature. In such an electronic appliance, it is necessary to prevent the high-temperature unit from being cooled more than needed while preventing the low-temperature unit from being affected by heat. However, there has been no conventional cooling system which can both maintain the high-temperature state in the high-temperature unit and prevent the rise in temperature of the low-temperature unit. Thus, conventional configurations have suffered from the problem of a number of units arranged in the electronic appliance failing to reliably exhibit their individual functions.
It is therefore an object of the present invention to provide a cooling system for an electronic appliance which can prevent the high-temperature unit, to be maintained at a high-temperature state, from being cooled more than needed while reliably preventing the low-temperature unit, to be absolutely prevented from temperature rise, from being affected by heat, and which permits multiple number of units to reliably exhibit their individual functions.
The present invention has been devised in order to achieve the above object, and the present invention is configured as follows:
In accordance with the first aspect of the present invention, a cooling system for an electronic appliance comprises: a high-temperature unit to be maintained in a predetermined high temperature state; a low-temperature unit to be kept from temperature rise; and a duct having an air flow passage for exhaust only created therein, and is characterized in that the whole or part of the duct is arranged between the high-temperature unit and the low-temperature unit.
In accordance with the second aspect of the present invention, the cooling system for an electronic appliance having the above first feature is characterized in that the low-temperature unit includes a heat source and at least the heat source of the low-temperature unit is exposed to the interior of the duct.
In accordance with the third aspect of the present invention, the cooling system for an electronic appliance having the above first feature is characterized in that the low-temperature unit includes a heat source and at least the heat source of the low-temperature unit is placed in contact with part of the duct.
In accordance with the fourth aspect of the present invention, the cooling system for an electronic appliance having the above first feature is characterized in that at least the portion of the duct, opposing a heat source of the low-temperature unit is formed of a high thermally conductive material.
In accordance with the fifth aspect of the present invention, the cooling system for an electronic appliance having the above third feature is characterized in that the duct has a top surface having a depressed portion into which the heat source projected downward from the bottom surface of the low-temperature unit is fitted from above.
In accordance with the sixth aspect of the present invention, the cooling system for an electronic appliance having the above third feature is characterized in that the duct has an upper interior surface having a radiating portion on the inner side thereof corresponding to the area opposing the heat source of the low-temperature unit.
In accordance with the seventh aspect of the present invention, the cooling system for an electronic appliance having the above first feature is characterized in that a radiating portion is formed on an interior surface perpendicular to the air flow passage inside the duct and the high-temperature unit and low-temperature unit are arranged in the direction perpendicular to the air flow passage with the duct interposed therebetween.
In accordance with the eighth aspect of the present invention, the cooling system for an electronic appliance having the above first feature is characterized in that an insulating portion is disposed between the duct and the high-temperature unit.
In accordance with the ninth aspect of the present invention, the cooling system for an electronic appliance having the above first feature is characterized in that the duct constitutes part of a frame supporting the units including the high-temperature unit and low-temperature unit.
In accordance with the tenth aspect of the invention, the cooling system for an electronic appliance having the above ninth feature is characterized in that at least part of the duct and frame is composed of a high thermally conductive material.
In the above first configuration, the high-temperature unit to be maintained in a predetermined high temperature state and the low-temperature unit to be kept from temperature rise are separated by the whole or part of the duct having an air flow passage for exhaust only created therein. Therefore, heat arising on the low-temperature unit side from the high-temperature unit is absorbed by the air passing through the air flow passage inside the duct and discharged therethrough, so that no heat will transmit to the low-temperature unit. Further, since the high-temperature unit is not in direct contact with the exhaust air, no heat will be removed from the high-temperature unit through the exhaust air.
In the above second configuration, at least the heat source of the low-temperature unit comes into contact with the exhaust air passing through the air flow passage created inside the duct. Therefore, heat arising from the heat source in the low-temperature unit is absorbed by the exhaust air and discharged thereby, so that no temperature rise will occur in the low-temperature unit. Further, the heat source as well as the areas to which heat from the heat source is transmitted can be brought into contact with the exhaust air passing through the air flow passage inside the duct, thus making it possible to reliably cool the low-temperature unit.
In the above third configuration, heat arising from a heat source in the low-temperature unit is absorbed via part of the duct by the exhaust air passing through the air flow passage created inside the duct and discharged thereby. Accordingly, heat arising from the heat source will not raise the temperature in the low-temperature unit. The duct defining the air flow passage for exhaust can be also be used as a supporting element for the low-temperature unit. Therefore, it is possible to cool the low-temperature unit by letting the exhaust air absorb the heat arising from the heat source in the low-temperature unit via part of the duct while realizing a simple supporting structure of the low-temperature unit.
In the above fourth configuration, heat arising from the heat source in the low-temperature unit is absorbed via the high thermally conductive portion of the duct by the exhaust air passing through the air flow passage created inside the duct and discharged thereby. Accordingly, heat arising from the heat source is efficiently absorbed by the exhaust air.
In the above fifth configuration, the heat source of the low-temperature unit is located in the depressed portion formed on the top surface of the duct. Accordingly, the whole surface of the area of the heat source exposed from the bottom surface of the low-temperature unit is placed opposite to the inner surface of the depressed portion formed on the top surface of the duct. Therefore, heat arising from the heat source can be efficiently absorbed via the depressed portion of the duct by the exhaust air.
Since the depressed portion into which the heat source of the low-temperature unit is accommodated has an inclined surface on the side opposing the exhaust air passing through the air flow passage, the exhaust air can be smoothly passed through the air flow passage without the flow of exhaust air in the air flow passage being obstructed. Since the cross section of the portion opposing the heat source of the low-temperature unit is reduced in the air flow passage, the velocity of flow of the exhaust air in this position increases, leading to efficient cooling of the heat source.
In the above sixth configuration, heat transmitted from a heat source of the low-temperature unit to the upper portion of the duct is absorbed via the radiating portion by the exhaust air. Accordingly, the heat transmitted to the top surface of the duct is efficiently absorbed by the exhaust air.
In the above seventh configuration, in the interior of the duct located between the high-temperature unit and the low-temperature unit, a radiating portion is formed on the surface parallel to the direction of the arrangements of the high-temperature unit and the low-temperature unit. Therefore, heat transmitted from the high-temperature unit to the duct whilst being transmitted from the high-temperature unit side to the low-temperature unit side in the duct, is absorbed via the radiating portion by the exhaust air, so that no heat will transmit to the low-temperature unit via the duct.
In the above eighth configuration, the insulating portion stops conduction of heat arising from the high-temperature unit to the duct. Therefore, no heat from the high-temperature unit will be absorbed via the duct by the exhaust air and discharged thereby.
Also, conduction of the heat arising from the high-temperature unit to the exhaust air passing through the air flow passage in the duct can be stopped by the portion of the duct on the high-temperature unit side, thus preventing reduction in temperature of the high-temperature unit. Further, there is no need to provide an extra insulating element between the high-temperature unit and the duct, thus making it possible to realize a compact configuration.
In the above ninth configuration, part of the frame is configured by the duct. Therefore, the frame supporting the units including the high-temperature unit and low-temperature unit is reinforced by the duct thus eliminating part of the elements constituting the frame.
In the above tenth configuration, the units including the high-temperature unit and low-temperature unit are supported by the duct and the frame, which are, at least, partially composed of a high thermally conductive material. Therefore, excessive heat arising from the high-temperature unit and from the low-temperature unit will efficiently transmit to the duct and the frame.